• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.306-306
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• 2007

최근, LED 구동 인버터, DC-DC 컨버터, AC-DC 컨버터 및 형광등 ballaster 등의 고전압전원장치등에 압전변압기를 적용하고자 하는 연구가 활발히 진행되고 있다. 순수한 $PbTiO_3$는 큐리온도($490^{\circ}C$)가 높고, 기계적강도가 크며, 비유전율(약 200 정도)이 작다. 또한, 두께방향 진동의 전기기계 결합계수 ($K_t$)가 윤곽진동의 전기기계 결합계수($K_p$)보다 크므로 두께방향의 진동모드를 이용한 벌크파 진동자의 경우 윤곽진동방향으로 불요신호(spurious signal)가 적고, 작은 grain size($1\;{\mu}m$정도)로 미세가공이 가능하여 고주파 재료로 이용되고 있다. 압전변압기의 출력 전력을 향상시키기 위해서는 적층으로 제작하여야 하는데 적층 압전변압기 제작시 층간의 내부 전극이 도포된 상태에서 소결하여야 한다. 이때 소걸 온도가 높으면 Pd 함랑이 높은 전극을 사용하여야 하는데 Pd 전극의 가격이 비싸 소자의 경제성이 떨어지게 된다. 따라서 순수한 Ag 전극을 내부전극으로 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결이 가능하여야 한다. 따라서 본 연구에서는 $(Pb,Ca,Sr)Ti(Mn,Sb)O_3$ 조성을 이용하여 $900^{\circ}C$ 이하의 저온소결이 가능한 두께방향진동모드 적층 압전변암기를 제작하여 그에 대한 전기적 특성을 조사하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.68-69
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• 2005

Low temperature ($\leq900^{\circ}C$) sintering piezoelectric ceramics $0.01Pb(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3-0.35PbTiO_3-0.23PbZrO_3+0.1wt%Y_2O_3+xwt%ZnO$ $(0{\leq}x{\leq}2.5)$ have been developed and investigated. The electromechanical coupling coefficient ($k_p$), piezoelectric constant ($d_{33}$), and mechanical quality factor ($Q_m$) have been measured to characterize the piezoelectric materials system. When 2.0 wt% ZnO is added, the properties of the system, $d_{33}$ = 559 pC/N, $k_p$ = 55.0 % and $Q_m$ = 73.4 are obtained which are very suitable for piezoelectric actuators. A bending mode multilayer actuator has been also developed using the materials which size is $27(L)\times9(W)\times1.07(t)mm^3$. The actuators are fabricated by multilayer ceramic (MLC) process and consist of24 layers and each layer thickness is $35{\mu}m$. At this time, the displacement of actuator was $100{\mu}m$ at 28V.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.57-62
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• 2023

This paper proposes a tri-band bandpass filter using dual-mode stepped-impedance resonators (SIRs) with parallel coupled structures. The proposed filter adopts U-shaped SIRs with open stubs and parallel coupled lines (PCLs) that have inter-digital and comb-line shorted ends. Two U-shaped SIRs with open stubs build the first and third passband, and the central PCL resonators build the second passband. Five resonators and coupling structures are theoretically analyzed to derive the scattering parameters of the proposed filter. A novel tri-band bandpass filter is designed and fabricated using the induced scattering parameters. The measured result of the fabricated tri-band bandpass filter shows a good agreement with the simulated one.

• Journal of Theoretical and Applied Mechanics
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• v.3 no.1
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• pp.34-44
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• 2002

Theoretical analysis Is carried out to identify the modal coupling effect between some particular acoustic modes of a vehicle compartment cavity and vibration modes of body panels like side doors, roof or floor. A simplified panel-cavity coupled model is investigated on the coupled resonance frequencies, modes and frequency response characteristics. Through parametric study, It Is possible to explain how the acoustic response of a coupled system will be determined by the vibration and acoustic property of the individual panel and cavity system. Full coupled system shows some interesting features different from those of the semi-coupled system In frequency, mode and acoustic response.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.5
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• pp.327-333
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• 2003

Several tests are performed to evaluate road booming noise. Baseline test delivers the information of road noise characteristics. Coupling effect between structure and acoustics is obtained from the mode shapes and the natural frequencies by the modal test. Equivalent stiffness at joint areas between chassis and car-body system can be determined by the input point inertance test. Noise sensitivity of body mounting point of a chassis part can be obtained from the noise transfer function test with input point inertance test. Operational deflection shape makes us analyze the actual vibration modes of the chassis system under actual leading and find noise sources very easily. Finally, the transfer path analysis is used to Identify noise Paths through the chassis system. The objectives and the procedures of the tests are described in this Paper Also, the guideline for efficient road noise evaluation test can be found.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.331-337
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• 2015

A novel fully-printed microstrip antenna with negative first resonance and dual polarization is proposed. The radiator is printed on the 1-layer substrate instead of multilayers. The -1st resonance results from a composite right- and left-handed(CRLH) structure that has a circumferentially interlocked gap capacitively coupling a patch with a shorted-ring. This compact antenna is provided with a dual-polarization capability by creating two orthogonal linear polarizations in one body with coaxial feeds. The design is carried out by doing full-wave EM field simulation which is compared with the measurement of the fabricated antenna prototype. The measured results give the gain of 5 dBi and the efficiency of 78% at the -1st resonance mode as the center frequency of a downlink channel of the bandwidth over 20 MHz with 29 dB polarization isolation for mobile communication.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.477-480
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• 2004

We studied the characteristics of impedance and electromechanical coupling coefficient in ZnO and AIN thin films by using resonance frequency spectrum method. The response peak of impedance decreased with the decrease of thickness of piezoelectrics, the number of mode of response peak increased with the increase of substrate thickness. An error of $k_{t}^{2}$ estimated from input $k_{t}^{2}$ increased as the thickness of piezoelectrics decreased and the thickness of substrate increased. Also, the error was increased in case of a large acoustic impedance of substrate. It was found that the composite resonator operating in optimized condition could be designed through the resonance frequency spectrum analysis of composited resonator consisted of piezoelectric thin film and substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.192-195
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• 1995

PZT powders were prepared by the molten salt synthesis method. The porous PZT was prepared from a mixture of PZT an polyvinylacohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The piezolectirc and acoustic properties with various PVA wt% were studied, Piezoelectric coefficient d$\sub$33/ of porous PZT ceramics was almost same to that of single phase PZT ceramics, The thickness mode coupling factor k$\sub$t/ was 0.53~0.59 in comparable with the single phase PZT ceramics(k$\sub$t/=0.7)

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.387-390
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• 1998

We propose comb-line filter using SIR(Stepped Impedance Resonator) with two transmission line. The coupling structure of the filter is double coupled line where two coupled lines are linked with cascade. We find out the inverter function of the filter. using even and odd mode impedance. The merits of the filter are that first, we can design transmission zero point at any frequency that we wanted without using lumped elements : chip capacitors and inductors. Second, we can design small size filters. To validate the inverter function of the filter with double coupled line we designed and fabricated two-pole band pass filter with the proposed filter structure.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.74-78
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• 1990

In this study, to develope the ultrasonic transducer element, the extrusion method which is the processing technique of the piezoelectric composite materials is introduced, the connectivity of the piezoelectric composite materials is the 1-3 type, and we study the properties of the materials. The electromechanical coupling factor(kt) of the materials is above 0.6, the resonance property(fr) is the thickness mode in the frequency range of 0.5 to 2 [MHz] and the acoustic impedance(Zac) is about 5 to 7 [Maryl]. From these results, it is known that the piezoelectric composite materials manufactured byt he extrusion method will be able to develope the ultrasonic transducer elements.